Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 31: Superconductivity: Fe-based Superconductors – 122 and 111
TT 31.3: Talk
Tuesday, March 17, 2015, 10:15–10:30, H 2053
Coaction of marginal Fermi liquid behavior and van Hove singularities in unconventional superconductors — •J. Fink1,6, A. Charnukha1, E.D.L. Rienks2, Z.H. Liu1, S. Thirupathaiah1, I. Avigo3, F. Roth4, H.S. Jeevan5, P. Gegenwart5, M. Roslova1, I. Morozov1, S. Wurmehl1,6, U. Bovensiepen3, S. Borisenko1, M. Vojta6, and B. Büchner1,6 — 1IFW Dresden Germany — 2HZB Berlin Germany — 3Universität Duisburg-Essen Germany — 4Center for Free-Electron Laser Science Hamburg Germany — 5Universität Augsburg Germany — 6TU Dresden Germany
Using ARPES we have studied the scattering rates and effective masses of the ferropnictides (Ba/Eu)Fe2(As1−xPx)2 and NaFe1−x(Co/Rh)xAs as a function of the control parameter (chemical pressure/ electron doping). The detected scattering rates of all electron and hole pockets are nearly independent of the control parameter, strongly differ for pockets having different orbital character, and are linear in energy indicating marginal Fermi liquid behavior near otimal substitution/doping. The measurements also indicate a crossing of the top of that hole pocket, having the largest scattering rate, through the Fermi level. A calculation as well as the experiments show that a coaction of marginal Fermi liquid behavior and the weakly dispersive band crossing the Fermi level leads to an extended singularity. The later can explain, possibly also in other unconventional superconductors, the strong mass enhancement near optimal doping/substitution and a superconducting phase with a small effective Fermi energy favoring a BCS-BE crossover state.